1. Field of the Invention
The present invention relates to a wing of composite material for constructing an aircraft airframe and a method of fabricating the same.
2. Description of the Related Art
An aircraft wing of composite material is constructed by assembling a lower skin, an upper skin, spars and ribs by using assembling jigs and fastening together the lower skin, the upper skin, the spars and the ribs by using fastening means. Alternatively, an aircraft wing of composite material is constructed by forming a combined structure of composite material integrally including a lower skin (or an upper skin), spars and ribs and fastening an upper skin (or a lower skin) to the combined structure by using fastening means.
The aircraft wing of composite material formed by fastening together the component members is a heavyweight structure comprising a large number of component parts. Since work for assembling the aircraft wing needs special assembling jigs, the aircraft wing is costly.
The aircraft wing constructed by using the combined structure having either the lower skin or the upper skin is based on the conventional concept of structure, jigs and processes are complicated and hence the aircraft wing is costly.
The present invention has been made in view of the foregoing circumstances. Therefore, a first object of the present invention is to provide a wing of composite material having a greatly reduced number of component parts, and capable of being assembled by greatly reduced manhours and of being fabricated at a low cost, and a method of fabricating such a wing.
Another object of the present invention to provide a wing of composite material having an improved appearance, and capable of being formed in dimensions of an improved accuracy, and a method of forming such a wing.
According to an aspect of the present invention, a wing of composite material comprisies: upper and lower skins, each of which has a root and a tip; and a plurality of intermediate spars arranged between the upper and the lower skins; wherein the plurality of intermediate spars extend from the roots to the tips of the upper and lower skins, and are integrally formed with or adhesively bonded to the upper and the lower skins.
Preferably the plurality of intermediate spars are provided with openings in their side walls, and reinforcing members are passed through the openings and are bonded to the upper and the lower skins and the intermediate spars.
Two additional spars may extend from the roots to the tips, on opposite sides of the intermediate spars, and may be bonded to the upper and the lower skins.
Preferably, the wing of composite material is an aircraft main wing, and the intermediate spars extend from a wing root toward a wing tip.
According to an aspect of the present invention, a method of fabricating a wing of composite material comprising an upper skin, a lower skin and a plurality of intermediate spars arranged side by side so as to extend from roots toward tips of the upper and the lower skins, comprises the steps of: forming through holes in side walls of the plurality of intermediate spars; disposing the plurality of intermediate spars on one of the skins so that the through holes are aligned with each other; disposing the other skin on the plurality of intermediate spars; integrally forming the plurality of intermediate spars and the skins or adhesively bonding together the plurality of intermediate spars and the skins; and passing reinforcing members through the through holes of the plurality of intermediate spars and bonding the reinforcing members to the plurality of intermediate spars and the skins.
Preferably, the step of forming through holes in side walls of the plurality of intermediate spars includes the steps of: forming portions in which any prepreg sheets are not superposed in prepreg structures by intermittently superposing prepreg sheets on a hollow heat-resistant rubber bag; closing the portions in which any prepreg sheets are not superposed with closing members; curing the prepreg structures formed by superposing prepreg sheets; and removing the closing members from the prepreg structures after curing.
Alternatively, the step of forming through holes in side walls of the plurality of intermediate spars includes the steps of: winding rovings around a laminating jig to form a roving structure; cutting out portions of the roving structure formed on the laminating jig to form openings; closing the openings with closing members; impregnating the roving structure with a resin and curing the resin-impregnated roving structure; and removing the closing members from the resin-impregnated roving structure after curing.
According to an aspect of the present invention, a wing of composite material comprises a plurality of intermediate spars of composite material each having upper and lower flanges forming sections of upper and lower skins, and a web formed integrally with and extending between the upper and lower flange; wherein the plurality of intermediate spars are united together so that surfaces of the upper and lower flanges form surfaces of the upper and the lower skin, respectively.
Preferably, each intermediate spar having the upper and the lower flanges and the web has a U-shaped cross section, adjacent intermediate spars are united together in such a manner that outer surfaces of portions of the flanges contiguous with an outer surface of the web of one of the intermediate spars are in contact with inner surfaces of edge portions of the flanges of the other intermediate spar, and the portions of the adjacent intermediate spars in contact with each other are fastened together with fasteners.
Preferably, the wing is an aircraft main wing, and the intermediate spars extend from a wing root toward a wing tip.
According to an aspect of the present invention, a wing of composite material comprises: upper and lower skins of composite material provided with stiffening parts on inner surfaces thereof, respectively; and flat plates extended between and united to the upper and the lower skin by adhesively bonding opposite edge portions thereof to the stiffening parts.
Preferably, the flat plates extend between a wing root and a wing tip.
Preferably, the number of the flat plates is at least three, and the flat plates are disposed in a parallel arrangement.
Preferably, each of the stiffening parts has a flat side surface to which a flat plate is bonded.
According to an aspect of the present invention, a method of fabricating a wing of composite material, comprises the steps of: forming upper and lower skins of a fiber-reinforced resin composite material having stiffening parts on inner surfaces thereof, respectively; placing the upper and the lower skin at an interval in a die; disposing flat plates between the upper and the lower skin in such a manner that upper and lower edge portions thereof face the stiffening parts, respectively; and uniting together the upper and the lower skin by adhesively bonding the upper and the lower edge portions of the flat plates to the stiffening parts.
According to an aspect of the present invention, a method of fabricating a wing of composite material comprises the steps of: forming upper and lower skins of a fiber-reinforced resin composite material having stiffening parts on inner surfaces thereof, respectively; placing the lower skin on a lower half die; disposing forming jig having pressing jigs and stretchable jig on the lower skin; disposing flat plates in such a manner that lower edge portions thereof face the stiffening parts of the lower skin, respectively; placing the upper skin on the forming jigs in such a manner that the stiffening parts thereof face upper edge portions of the flat plates, respectively; placing an upper half die on the upper skin; clamping together the upper and the lower half die; and pressing the upper skin against an inner surface of the upper half die and pressing the upper and the lower edge portions of the flat plates against the stiffening parts of the upper and the lower skin to unit together the upper and the lower skin.